Association Between Muscle Quality and GNRI in Patients with Type 2 Diabetes

<b>Background:</b> Type 2 diabetes (T2D) has been linked to impairments in skeletal muscle performance, encompassing reductions in both muscle strength and muscle quality. While malnutrition is a known modifiable factor contributing to muscle quality deterioration, its specific relationship with the Geriatric Nutritional Risk Index (GNRI) in T2D remains underexplored. Using data from 743 participants in the KAMOGAWA-A cohort, this cross-sectional study evaluated the association between muscle quality and GNRI in individuals with type 2 diabetes. <b>Methods:</b> Muscle quality was defined as handgrip strength divided by arm lean mass. GNRI was calculated using serum albumin and body mass index. Multiple linear regression models were used to assess associations between GNRI and muscle quality. To account for BMI-related dependency in muscle quality measurements, we derived BMI-adjusted GNRI residuals and performed the same regression analysis to evaluate the stability of the observed relationship beyond BMI-induced confounding. <b>Results:</b> In the overall population, GNRI was inversely associated with muscle quality (β = -0.17, <i>p</i> < 0.001). Conversely, residual GNRI demonstrated a significant positive association with muscle quality (β = 0.13, <i>p</i> < 0.001), especially among men, individuals under 65 years of age, and across all BMI categories. Stratified analyses suggested that the strength and direction of associations varied by age, sex, and glycemic control status. <b>Conclusions:</b> The GNRI showed an inverse correlation with muscle quality, whereas residual GNRI showed a consistent positive relationship. These findings suggest that improving nutritional status may support muscle function in T2D, but BMI confounds the interpretation of GNRI in this context.